/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cglib.core;

import net.sf.cglib.core.ClassGenerator;
import net.sf.cglib.core.DefaultGeneratorStrategy;

/**
 * CGLIB GeneratorStrategy variant which exposes the application ClassLoader
 * as current thread context ClassLoader for the time of class generation.
 * The ASM ClassWriter in Spring's ASM variant will pick it up when doing
 * common superclass resolution.
 *
 * @author Juergen Hoeller
 * @since 5.2
 */
public class ClassLoaderAwareGeneratorStrategy extends DefaultGeneratorStrategy {

    private final ClassLoader classLoader;

    public ClassLoaderAwareGeneratorStrategy(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }

    @Override
    public byte[] generate(ClassGenerator cg) throws Exception {
        if (this.classLoader == null) {
            return super.generate(cg);
        }

        Thread currentThread = Thread.currentThread();
        ClassLoader threadContextClassLoader;
        try {
            threadContextClassLoader = currentThread.getContextClassLoader();
        } catch (Throwable ex) {
            // Cannot access thread context ClassLoader - falling back...
            return super.generate(cg);
        }

        boolean overrideClassLoader = !this.classLoader.equals(threadContextClassLoader);
        if (overrideClassLoader) {
            currentThread.setContextClassLoader(this.classLoader);
        }
        try {
            return super.generate(cg);
        } finally {
            if (overrideClassLoader) {
                // Reset original thread context ClassLoader.
                currentThread.setContextClassLoader(threadContextClassLoader);
            }
        }
    }

}
